The self-alignment of integrated circuit parts, for example a trench self-aligned with a polysilicon line, is sometimes difficult to achieve.
Furthermore, the production of patterns is generally employed in so-called “double patterning” techniques. This “double patterning” technique is used when wishing to create patterns having dimensions smaller than the etching resolution allowed by photolithography. In this case, one conventional solution consists in using two photolithography steps, combined with depositions of sacrificial layers of material, so as to finally reduce in particular the spaces between the patterns created.
However, such a technique has the drawback of using two photolithography masks, with risks of overlay between the masks and ultimately the various elements of the patterns produced.
Another solution for transferring patterns in an integrated circuit consists in using a technique known to the person skilled in the art by the term SIT: “Sidewall Image Transfer”.
Here again, such a technique is used when the lithography tools reach their limit of resolution. This so-called SIT technique makes it possible to obtain spaces between the trenches which are much smaller than those which would have been obtained with a single photolithography mask. This technique thus consists in the formation of spacers on the sidewalls of intermediate elements defined by masking, then removal of these intermediate elements and transfer into the underlying substrate by etching, using the spacers as an etching mask. Although such a technique uses only one photolithography mask, it nevertheless involves numerous steps.